Mix together the red and green cabbage, green onions, cilantro, carrots and bell pepper in a large bowl. Toss to combine.
Rub the tuna with sunflower oil. Over medium-high heat, heat a large skillet. Add the tuna and cook 3 minutes per side to sear so that it is rare in the center and golden brown on the outside.
Meanwhile, for the dressing, add the rice wine vinegar, garlic, ginger, toasted sesame oil, soy sauce, sriracha, honey and olive oil to a small bowl. Mix to combine. Drizzle on the salad and toss gently to combine. Plate on a platter.
Slice the tuna into 1/2-inch slices and top the salad with the tuna. Sprinkle with the cashews, sunflower seeds and Aleppo pepper. Squeeze over a wedge of lime and serve the remaining lime wedges on the side.